Through the Portal
by VictoriaFirewraith
Summary: Undertale/Underfell AU Crossover As Frisk is running away from Papyrus, she goes through a strange looking door, only to find herself in another world where her counterpart there has made friends with those she could not...but what happens when Papyrus follows her through the portal for her soul?


Running footsteps echoed through the cave corridor, darkened gems glittered the wall as a fast moving shadow went past. A small girl, battered and bruised, held tight to a pot containing a yellow flower. Behind them, somewhere in the darkness, a red eye glowed.

"Frisk! He's still after us!" The Flower shrieked at the girl. Frisk tightened her grip on the pot, her feet still running.

"I k-know, Flowey," Frisked breathed, with heavy gasps.

"NO MATTER WHERE YOU RUN, HUMAN!" A voice shouted from behind them, "I WILL CATCH YOU AND KILL YOU!"

Frisk's body was burning with adrenaline, she could not stop, knowing that, perhaps this time, he will actually kill her. She tried her best to become friends with the skeleton, but she failed. Her Determination and kindness wasn't enough to turn him, to become her friend.

Frisk stopped mid-way as a rumble with through the cavern, shaking the floor. There were no sounds of footsteps behind her, he must have stopped as well. Dust and small rocks fell from the ceiling. Taking a deep breath, Frisk started to run again. The being behind her must have noticed and started to chase her again.

Up ahead, the corridor branched into three ways. The flower noticed this, "Oh dear...I never been this way before," he said nervously, "Take the the left, Frisk!" He yelped as Frisk quickly moved to the side, grinding into the corner wall as a blue bone went flying.

"I'M GAINING ON YOU HUMAN!" The voice growled, sounding closer then he was earlier. The corridor she ran into soon opened up and she was running on a bridge with lava flowing far underneath.

"W-we are in the Hotlands?!" Flowey gasped, glancing over Frisks protecting arm, watching the lava flow beneath them. The fires of the lava brightened the room as Frisk glanced over her shoulder to finally see the skeleton behind her clearly. He was tall, with black armor and red cape, the ends were torn and flying behind him. He also wore red gloves and boots. A single eye was glowing red with anger and power.

"THIS WILL BE THE END OF YOU HUMAN!" He yelled, "I, THE GREAT PAPYRUS, WILL DO SO!"

With a small yelp, Frisk ran faster, wanting to get over the bridge before Papyrus got any ideas. She was grateful when she landed on solid land. Flowey started to shake in his pot as blue bones came flying at them. Frisk barely dodged them. She yelped in pain as one hit her square in the back. With Determination, she kept on running despite the pain.

She turned into another hall on her right. Her eyes widened slightly, at the end was another Skeleton, shorter than the other one, he wore a black jacket with white fuzz on the ends with a red shirt underneath and black shorts with a single yellow stripe running down them. A single gold tooth glinted in the light.

"Hey kid," He waved at her with an evil grin as he blocked her way. Frisk skidded to a halt, a mere few feet away from him.

The steps behind her stopped, "GOOD JOB SANS! YOU STOPPED THE HUMAN!"

Flowey looked over Frisk's shoulder and gasped, there behind them was Papyrus.

"Uh yeah," San's replied.

"FINALLY! WITH YOUR SOUL, I, THE GREAT PAPYRUS, CAN FINALLY BECOME CAPTAIN OF THE ROYAL GUARD AND BE STRONGER THAN UNDYNE!" Papyrus spoke as he walked towards Frisk, a bone in his hands.

Frisk had nowhere to go, she was stuck between the skeleton brothers. She weighed her options as Papyrus walked closer to her. Flowey shook so much in fear, that it was shaking Frisk. She glanced down at her friend and back to the skeleton coming at her. With new Determination, she held Flowey with one held and brought out her concealed knife and made a run towards Sans.

Surprised at her sudden movement to him, he flinched and she got past him.

"SANS! YOU IDIOT! DON'T LET HER GET AWAY!" Papyrus growled at his brother.

"Yeah, of course," Sans replied, as he brother ran passed him.

The place once again started to shake, this time a bit more violently. Frisk barely kept her balance as she ran. Somewhere in the distance amidst the rumbling, there was a spark of light. Grimacing, having nothing else to do, she headed towards the light, hoping it will get her to safety. She turned another corner and stopped.

In front of her was some sort of entrance, it looked more like a doorway with light framing the edges. Something shimmered on the surface, almost like water ripples.

"I don't think we should go in there," Flowey said.

"We have nowhere to go, Flowey, besides...Papyrus is right behind us," Frisk replied.

"Right...It's the only way left to go," Flowey said solemnly.

Gripping the pot and with Determination, Frisk ran through the strange opening, tripping over her own feet and letting Flowey go. She heard he pot roll away and a set of footsteps coming towards them….is this the end?

* * *

Frisk finally returned to her friends after traveling through Home telling her other friends goodbye. Toriel was joking around with Sans, Undyne was chatting with Asgore and Alphys was messing around with a weird, small box with a big red button.

Frisk went to talk to to each one of her friends again, before they leave the underground. Toriel left her some text messages on her phone, Sans joked about being to busy because he had work, Undyne wanted to see some new anime, Alphys is gonna write some fan fiction and Asgore offer her some tea.

Frisk smiled at her friends, deciding it was time for them to leave and head for the barrier. As she lead the way, Papyrus noticed the strange box Alphys was holding.

"WHAT'S THAT? IT LOOKS COOL!" Papyrus said, glancing over Alphys small frame. She flinched as the skeleton came closer.

"A-ah well, y-you see...it's a mechanical box I just created on a whim. I-I have no idea what it does...I just wanted to make o-one last thing down here," Alphys explained.

"Whatever you make is always awesome," Undyne said, causing Alphys to blush, "Except Mettaton, he annoys me," she muttered under breath so Alphys wouldn't catch it.

"I guess you really thought outside the box on that one," Sans replied after Undyne, with Toriel snickering slightly.

Papyrus rolled his eyes at his brothers lame joke, he than reached over Alphys and took the metal box.

"A-ah! I don't think i-it's ready for others to touch!" Alphys gasped.

"PREPOSTEROUS! EVERYTHING IS READY FOR ME TO TOUCH, SINCE I AM THE GREAT PAPYRUS!" and with that, Papyrus pressed the red button on the strange box. A strange light erupted from the box and the earth started to shake.

"Ahhh, Oh no!" Alphys yelped, "What's happening?!"

"YOU MADE IT!" Papyrus yelped, tossing the box away. It landed with a thud a bit away.

During the small earthquake, Toriel brought Frisk into her arms, protecting from anything that might have fallen from the ceiling. Sans had fallen on his behind and Undyne got ready for battle. Soon the quaking stop and everyone uncovered their heads. Frisk untangled herself from Toriel's grasp and glanced around.

Where Papyrus threw the box was now a strange doorway, with blue light on the fringes. Frisk took a few careful steps towards the strange thing.

"Ah Frisk, wait!" Alphys said, walking forward to check out the strange thing that appeared, "How e-extraordinary!"

"What happened?" Asgore asked, glancing at the thing.

Alphys took a look around the thing walking behind it, "Interesting, I think I might have made a doorway to some other place,"

"Really?! Is it a world with Robots? Fighting? Princesses? FIGHTING ROBOT PRINCESSES?!" Undyne gasped. Alphys sweated a little under the odd pressure Undyne was putting unto her about certain anime subjects that another world might contain.

"I do not know," Alphys replied as she walked back to the group.

"Maybe we should just ignore it," Toriel said when the portal started to ripple and someone came through. It was a small person who tripped over their own feet, landing face first. Something flew out of their hands and rolled towards them. It was a pot with a yellow flower in it. It shook its head, probably shaking off the pain. The flower lifted it's head to see Papyrus walking towards him, the flower paled.

"HEY! IT'S THE FLOWER!" Papyrus said. Alphys gasped, realizing who it was.

"P-P-Papyrus! Get away from that flower!" Alphys yelped. Frisk couldn't understand what was happening, she thought that Flowey had become Asriel and would stay that way.

Flowey shook in his pot, scared that Papyrus had finally caught up with them, despite the strange garb he was wearing, he was still scared, "Frisk! Help!"

Frisk tilted her head at his cry of help, so did the others till the other person who came through the portal stood up, revealing to be Frisk, but more bruised looking. Frisk rushed toward the flower grabbing his pot and walking backwards away.

"I-I don't understand," Toriel gasped, "Why is there another Frisk?!"

"I-I must have actually created a door to another world!" Alphys beamed.

"What about the robot's?" Undyne grumbled.

Toriel noticed the fear in the other Frisk's eye's and wandered why. Their Frisk walked forward to the other one, watching her. The two seemed to talk without actually speaking as Flowey glance between the two, he was slightly confused why their was another Frisk, unless….it was Chara.

"I see," Frisk nodded.

"What's going on, my child?" Toriel asked, the other Frisk flinched at her worlds. Their Frisk turned to them.

"Well….," Frisk started to ask, when Undyne interrupted.

"You are from another world! Are their Robot's their?!" Undyne said giddily.

The other Frisk stood there, staring at Undyne, shaking her head slowly. Flowey stood up tall, despite being in a pot, "L-listen, you! I don't know how we got here, but we gotta go. We gotta go Frisk, before-,"

"I don't know how y-your world is, but I wouldn't trust that flower," Alphys spoke up.

"What?!" Flowey gasped.

Frisk looked down at her friend, "Why not? He has been the only one helping me," She was still wary of these 'Clones' that stood before her, but they don't seem to be like the ones she know.

"Your only friend?" Toriel asked, "If you are from an...alternative world, wouldn't we still be your friends?"

Frisk shivered as she heard a familiar voice coming from behind her.

"HUMAN! NO MATTER WHERE YOU RUN, I WILL FIND YOU!"

"That sounds like Papyrus!" Undyne said turning her attention to the portal, so did the others. Through the portal came the other worlds Papyrus, though he was wearing darker clothing than their own Papyrus.

The other stared down at the two Frisk's, "TWO HUMANS?!"

The other Frisk shook where they stood and decided to hide behind Frisk. The others were surprised to see another Papyrus, except for Undyne who just rolled her eyes.

"I SEE MY GREAT SELF EVEN GRACES ANOTHER WORLD!" Papyrus said, smiling.

If Skeletons had eyebrows, Evil Papyrus would've raised them, "ANOTHER PAPYRUS? WHAT TRICK ARE YOU PLAYING HUMAN?"

"This is no t-trick," Alphys stuttered, "I somehow c-created a doorway between our worlds and you three just happened to walk through,"

Evil Papyrus stared down at Alphys, ' _A DIFFERENT WORLD? THAT MEANS...TWO HUMAN SOULS I CAN TAKE_ ,' he turned his attention to the the two Frisks.

"Frisk," Flowey gulped, "Run!"

Frisk glanced over at her counterpart than back at Evil Papyrus.

"WITH TWO HUMAN SOULS, I WILL BECOME EVEN MORE POWERFUL," Evil Papyrus said, a bone scythe appearing in his hands, taking a swing at the two humans. Toriel was able to pull the two away, just missing the swing.

"What are you doing?! You could hurt them!" Toriel almost screeched.

"THAT'S THE PLAN! WITH TWO HUMAN SOULS, I, THE GREAT PAPYRUS CAN BECOME HEAD OF THE ROYAL GUARD! MAYBE..EVEN MORE!" His left eye started to glow red and swung again.

"That's some ambitious talk there," Undyne said, countering his attack.

"UNDYNE!" Evil Papyrus said, "EVEN HERE YOU GO AGAINST ME!"

"I'm guessing we're not quite fond of each other back in your world," Undyne said.

"Oh dear," Asgore said.

"Agreed, This is turning out weird," Sans replied, "a world...where we..are evil?" He glanced down at his own hand.

Toriel hugged the other Frisk, "I can see why you looked like you were scared of us," Frisk wasn't too sure about this, getting hugged by the same person who tried to lock her away in the ruins, abusing her, but for some reason, this felt right with her. Flowey calm down a little seeing that the other were trying to protect them.

Undyne and Evil Papyrus were clashing, but it seem that Evil Papyrus got the upper hand as he used his special move. Undyne glowed blue and she thrown away.

"HAH! YOU ARE WEAKER THAN THE UNDYNE I KNOW!"

Undyne growled as he said this, getting back to her feet, but Evil Papyrus did the same move again and again.

"SANS!" Papyrus whispered to his brother,"WHAT DO WE DO?" he whispered.

Sans himself wasn't sure what to do, they can join Undyne fighting, but they'll most likely get in the way. Evil Papyrus is definitely stronger than his own brother, putting up a good fight against Undyne. As he was thinking, Asgore decided to take a stance against the evil Skeleton.

On the other side of the Portal, Sans stood there, watching ripples go across the strange opening. Papyrus had went in there to chase after the human.

Sans thought of all the times he killed the kid, but they still came back, asking to be his friend, "Monsters can't be friends with humans," He murmured, thinking back to the times they showed him mercy.

"Damn it all, Kid...why do you keep coming back? My brother is out to kill you," he said, knowing no one was listening. He also remembered what Undyne once said to him, That his brother will never become Captain of the Royal, even less join it.

He knew he was always in his brother's way and he hated it.

But there was something about that child...and he was filled with determination.

"NYEH HEH HEH HEH! I HAVE DEFEATED CLONE UNDYNE AND CLONE ASGORE! ONLY YOU FOUR STAND IN MY WAY!" Evil Papyrus said gleefully, "SOON ALL WILL WORSHIP THE GROUND I WALK ON WHEN I BRING NOT ONE, BUT TWO HUMANS!"

"I WON'T LET YOU TAKE MY FRIENDS!" Papyrus stood in front of the two Frisks, despite his legs shaking.

"Papyrus," Sans hissed.

Flowey and Frisk stared at the skeleton before them, through all there resets, no one had really stood up for the two as they made their way through the underground, attacked by Monsters. It made Frisk a little bit happy.

Evil Papyrus was about to attack Papyrus when another voice chimed in.

"Uh, hey bro," Behind Evil Papyrus was Evil Sans.

"A CLONE OF MY BROTHER!?" Papyrus gasped and Sans just stared at his counterpart, noticing somehow a skeleton was sweating.

"AH SANS! GOOD OF YOU TO COME! I COULD USE YOUR HELP!" Evil Papyrus lowered his weapon.

"Yea...about that," Evil Sans rubbed the back of his head, "how about we just let the kid go?" he wasn't sure what was happening with the doubles of people, but he just needed to convince her bro to let the kid go.

"WHAT?! WHY?! THAT HUMAN IS MY ONLY CHANCE!" Evil Papyrus yelled at his brother. Evil Sans flinched.

"HEY! YOU SHOULDN'T TALK TO YOUR BROTHER LIKE THAT!" Papyrus said, but cowered a bit under Evil Papyrus gaze. He turned back to his brother.

"WHY?"

Evil Sans sweated nervously, "Well….I thought...I killed them so many times," Toriel gasped, "but they keep coming back and trying to make nice...maybe we should….I don't know...try..,"

"TRY?!" Evil Papyrus gasped, "I, THE GREAT PAPYRUS, DOESN'T DO 'FRIENDS',"

Hearing this, Frisk stood up, still holding onto Flowey. She walked around Toriel and Frisk, dodging their gasps. Flowey whispered that this wasn't a good idea and she should go back to the defense, but she ignore him.

Evil Papyrus turned from his brother to see Frisk smiling at him, "I still forgive you, can you please be my friend?"

"FORGIVE ME? DON'T YOU KNOW WHO I AM? I AM PAPYRUS THE GREAT! AND WHEN KILL YOU, PEOPLE WILL WORSHIP THE GROUND I WALK UPON,"

Frisk gazed up at him, still smiling.

"STOP THAT! STOP GIVING ME THAT LOOK!" Evil Papyrus raised his hand and Frisk heart symbol turned blue. Papyrus, Toriel and Alphys gasped, "I DON'T NEED FRIENDS!"

He threw a bone at her, but missed. He stared at her before he started to fume, "AGGHH!" He stomped away, back into the portal. Frisk fell down, Toriel and the other Frisk rushed towards her, asking if she was alright.

Frisk nodded yes and glance up at Evil Sans.

"Well...that was something….," he glanced around the room, Asgore and Undyne were finally able to get back up and he hated the stares he was getting from the other two skeletons that looked like him and his brother, "I...don't know what exactly was happening here...but you'll get through my brother...one day,"

"Hmph," Toriel turned to him, "How can you even think about attacking a child, even killing one?"

Evil Sans shrugged, "It's my job,...I guess..I should go back...this is already awkward," before anyone could say anything, Evil Sans stepped back through the portal after his brother.

Toriel glance down at the other Frisk, "Don't worry dear, it's all right now it seems," as she said that Frisk stood up, dust the dirt off and picked up Flowey and stared at the portal.

"Y-you're not thinking of going back, are you?" Alphys said. Frisk nodded.

"Those monsters harmed you, why would you even go back?!" Toriel gasped.

Frisk glanced over her shoulder and just smiled. Before walking back into the portal, Frisk felt a tap on her shoulder, it was the Frisk of this world. She gave her a thumbs and Frisk gave one right back at her.

As Frisk and Flowey disappeared into the portal, Alphys rushed to close it, pushing on the red button. The portal disappeared with a zap and Alphys gave a sigh of relief.

"DON'T KNOW ABOUT YOU GUYS, BUT THAT WAS SORTA WEIRD,"

* * *

"You know...you could've stayed," Flowey said, "They are definitely the nice versions,"

Frisk shook her head again, "No, this is the world I live in...and besides….I'm close to getting Papyrus to be my friend,"

 _ **The End.**_

 **A/N: Hello everyone, hope you enjoyed this. I just entered the Undertale fandom and love it {I got the game, but haven't played yet...my only source is Cry plays and Tumblr}**

 **Anywho...Thought it be interesting to see what happens when Undertale and Underfell collide...and I got this lil story...was somewhat based on some pictures I saw to help with the Underfell parts (but can't go wrong in Underfell since everything is up to our imagination for that}**


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